Glass sheet composite

ABSTRACT

The present invention is a glass sheet composite in which the loss coefficient is 1×10−2 or more and the longitudinal wave acoustic velocity in the sheet thickness direction is 5.5×103 m/s or more.

TECHNICAL FIELD

The present invention relates to a glass sheet composite having goodacoustic performance and also relates to a diaphragm, an opening member,and a glass substrate for magnetic recording mediums, each using theglass sheet composite.

BACKGROUND ART

Generally, a cone paper or resin has been used as a diaphragm forloudspeakers or microphones. Such a material has a high losscoefficient, making resonant vibration unlikely, and in turn, isregarded as having good sound reproduction performance in the audiblerange.

However, since the acoustic velocity is low in any of these materials,when the material is excited to vibrate at a high frequency, thevibration thereof is less likely to follow the acoustic wave frequency,and divided vibration is readily generated. It is therefore difficult tooutput a desired sound pressure particularly in a high-frequency range.

In recent years, the range required to be reproduced particularly for ahigh-resolution sound source, etc. is a high-frequency region of 20 kHzor more. This region is a range supposed to be poorly audible by humanear, but it is preferred that the sonic vibration in the range above canbe reproduced with high fidelity, because a stronger emotional impact ispresented, for example, a realistic sensation is felt strongly.

Accordingly, it may be conceived to use, in place of the cone paper orresin, a material having a high acoustic velocity propagating in thematerial, such as metal, ceramic and glass. However, in all of thesematerials, the loss coefficient is generally as small as approximatelyfrom 1/10 to 1/100 of that of paper and in turn, unintended reverberantsound is likely to remain. Furthermore, when a member is excited tovibrate at its intrinsic vibration frequency, conspicuous tonaldegradation may occur due to generation of a resonant mode.

BACKGROUND ART DOCUMENTS Non-Patent Literature

-   -   Non-Patent Literature 1: Olivier Mal et. al., “A Novel Glass        Laminated Structure for Flat Panel Loudspeakers”, AES Convention        124, 7343.

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

A laminated glass having a 0.5 mm-thick polybutyl polymer layer betweentwo glass sheets is known as a diaphragm for loudspeakers (Non-PatentDocument 1). However, reproduction in a high-frequency region has beendifficult for this diaphragm.

An object of the present invention is to provide a glass sheet compositehaving good acoustic performance.

Means to Solve the Problems

As a result of many intensive studies, the present inventors have foundthat the problem above can be solved by constructing a predeterminedglass sheet composite, and have accomplished the present invention.

<1> A glass sheet composite having a loss coefficient at 25° C. of1×10⁻² or more and a longitudinal wave acoustic velocity in a sheetthickness direction of 5.5×10³ m/s or more.

<2> The glass sheet composite according to <1>, including two or moreglass sheets and a liquid layer between at least a pair of glass sheetsout of the glass sheets.

<3> The glass sheet composite according to <2>, in which a thickness ofthe liquid layer is 1/10 or less of a total thickness of the pair ofglass sheets when the total thickness of the pair of glass sheets is 1mm or less, and 100 μm or less when the total thickness of the pair ofglass sheets is more than 1 mm.<4> The glass sheet composite according to <2> or <3>, in which theliquid layer has a viscosity coefficient at 25° C. of 1×10⁻⁴ to 1×10³Pa·s and a surface tension at 25° C. of 15 to 80 mN/m.<5> The glass sheet composite according to any one of <2> to <4>, inwhich both of at least a pair of glass sheets out of all the glasssheets have a specific modulus of 2.5×10⁷ m²/s² or more.<6> The glass sheet composite according to any one of <2> to <5>, inwhich out of two glass sheets constituting the pair of glass sheets,denoting Qa and wa respectively as a resonant frequency and a half-widthof resonance amplitude of one glass sheet A and denoting Qb and wbrespectively as a resonant frequency and a half-width of resonanceamplitude of the other glass sheet B, following relationship of [formula1> is satisfied:(wa+wb)/4<|Qa−Qb|  [formula 1]<7> The glass sheet composite according to any one of <2> to >6>, inwhich a mass ratio of two glass sheets constituting the pair of glasssheets is from 0.8 to 1.25.<8> The glass sheet composite according to any one of <2> to <7>, inwhich a sheet thickness of each of two glass sheets constituting thepair of glass sheets is from 0.01 to 15 mm.<9> The glass sheet composite according to any one of <2> to <8>, inwhich the liquid layer contains at least one member selected from thegroup consisting of propylene glycol, dimethyl silicone oil, methylphenyl silicone oil, methyl hydrogen silicone oil, and denaturedsilicone oil.<10> The glass sheet composite according to any one of <1> to <9>,including at least either one of physically strengthened glass sheet orchemically strengthened glass sheet.<11> The glass sheet composite according to any one of <1> to <10>, inwhich a visible light transmittance is 60% or more.<12> The glass sheet composite according to any one of <2> to <11>,including three or more glass sheets.<13> The glass sheet composite according to any one of <2> to <12>, inwhich at least one glass sheet or the liquid layer is colored.<14> The glass sheet composite according to any one of <2> to <13>, inwhich the liquid layer contains a fluorescent material.<15> The glass sheet composite according to any one of <1> to <14>, inwhich a coating or a film is formed on at least one of the outermostsurfaces of the glass sheet composite.<16> The glass sheet composite according to any one of <1> to <15>, inwhich the glass sheet composite has a curved surface shape.<17> The glass sheet composite according to any one of <2> to <16>, inwhich a difference between a refractive index of the liquid layer andthe refractive index of each of the pair of glass sheets is 0.2 or less.<18> The glass sheet composite according to any one of <1> to <17>, inwhich at least part of an outer circumferential edge surface of theglass sheet composite is sealed by a member not hindering vibration ofthe glass sheet composite.<19> A glass sheet composite including two or more glass sheets and aliquid layer between at least a pair of glass sheets out of the glasssheets, in which a thickness of the liquid layer is 1/10 or less of atotal thickness of the pair of glass sheets when a total thickness ofthe pair of glass sheets is 1 mm or less, and 100 μm or less when thetotal thickness of the pair of glass sheets is more than 1 mm.<20> A diaphragm including the glass sheet composite according to anyone of <1> to <19> and at least one vibrator disposed on one side orboth sides of the glass sheet composite.<21> An opening member using the glass sheet composite according to anyone of claims 1 to 19 or the diaphragm according to <20>.<22> A glass substrate for magnetic recording mediums, using the glasssheet composite according to any one of <1> to <19>.

Advantages of the Invention

According to the present invention, for example, in the application as adiaphragm used for loudspeakers, microphones, earphones, mobile devices,etc., sound reproducibility over the region from a low sound range to ahigh-frequency range is improved. In addition, for example, in theapplication as an opening member for buildings and vehicles, resonancecan be made to hardly occur at all by utilizing its high vibrationdamping capability and in turn, generation of an abnormal noiseattributed to resonance can be prevented. Furthermore, for example, inthe application as a glass substrate for magnetic recording mediums, thevibration control effect can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating one example of the glasssheet composite of the present invention.

FIG. 2 is a cross-sectional view illustrating another example of theglass sheet composite of the present invention.

FIG. 3 is a cross-sectional view illustrating still another example ofthe glass sheet composite of the present invention.

FIG. 4 is a perspective view illustrating yet still another example ofthe glass sheet composite of the present invention.

FIG. 5a is a plan view of the glass sheet composite of FIG. 4, and FIG.5b is a cross-sectional view along line A-A′ in FIG. 5 a.

FIG. 6 is a cross-sectional view illustrating another example of theglass sheet composite of the present invention.

FIG. 7a is a plan view illustrating another example of the glass sheetcomposite of the present invention, and FIG. 7b is a cross-sectionalview along line A-A′ in FIG. 7 a.

FIG. 8a is a plan view illustrating another example of the glass sheetcomposite of the present invention, and FIG. 8b is a cross-sectionalview along line A-A′ in FIG. 8 a.

FIG. 9 is a cross-sectional view illustrating still another example ofthe glass sheet composite of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Details and other features of the present invention are described belowbased on embodiments of the present invention. Here, in the followingdrawings, the same or corresponding reference numeral is assigned to thesame or corresponding members or parts, and duplicated description isthereby omitted. In addition, unless specifically indicated, thedrawings are not intended to show a relative ratio among members orparts. Accordingly, specific dimensions may be properly selected in thecontext of the following non-limiting embodiments.

Furthermore, “-” indicating a numerical range in the present descriptionis used in the sense of including the numerical values set forth beforeand after “-” as the lower limit value and the upper limit value,respectively.

<Glass Sheet Composite>

The glass sheet composite according to the present invention has theloss coefficient at 25° C. of 1×10⁻² or more and the longitudinal waveacoustic velocity in the sheet thickness direction of 5.5×10³ m/s ormore. Here, a high loss coefficient means that the vibration dampingcapability is high.

As for the loss coefficient, a value calculated by a half-width methodis used. Denoting f as the resonant frequency of a material and W as afrequency width at a point decreased by −3 dB from the peak value of theamplitude h (namely, the point of maximum amplitude −3 [dB]), the losscoefficient is defined as a value represented by {W/f}.

In order to prevent the resonance, the loss coefficient may beincreased, namely, this means that the frequency width W becomesrelatively large with respect to the amplitude h and the peak becomesbroader.

The loss coefficient is a characteristic value of a material, etc. and,for example, in the case of a simplex glass sheet, it differs dependingon the composition, relative density, etc. Incidentally, the losscoefficient can be measured by a dynamic modulus test such as resonationmethod.

The longitudinal wave acoustic velocity means a velocity at which alongitudinal wave propagates in a diaphragm. The longitudinal waveacoustic velocity and the Young's modulus can be measured by anultrasonic pulse method described in Japanese Industrial Standards(JIS-R1602-1995).

In the glass sheet composite according to the present invention, as aspecific configuration for obtaining a high loss coefficient and a highlongitudinal wave acoustic velocity, it is preferable to include two ormore glass sheets and include a predetermined liquid layer between atleast a pair of glass sheets out of the glass sheets.

(Liquid Layer)

The glass sheet composite according to the present invention can realizea high loss coefficient by providing a layer formed of a fluid (liquidlayer) between at least a pair of glass sheets. Among others, when theviscosity and surface tension of the liquid layer are set to suitableranges, the loss coefficient can be more increased.

This is considered attributed to the fact that, unlike the case ofproviding a pair of glass sheets with an adhesive layer therebetween,the pair of glass sheets are not fixed and continue exhibiting vibrationcharacteristics of each individual glass sheet.

The liquid layer preferably has a viscosity coefficient at 25° C. of1×10⁻⁴ to 1×10³ Pa·s and a surface tension at 25° C. of 15 to 80 mN/m.If the viscosity is too low, vibration can be hard to transmit, and ifit is too high, a pair of glass sheets located on both sides of theliquid layer are fixed to each other and exhibit a vibration behavior asone glass sheet, making damping of resonant vibration difficult. If thesurface tension is too low, the adhesion between glass sheets decreases,and vibration can be hard to transmit. If the surface tension is toohigh, a pair of glass sheets located on both sides of the liquid layerare readily fixed to each other and exhibit a vibration behavior as oneglass sheet and in turn, the resonant vibration is difficult to damp.

The viscosity coefficient at 25° C. of the liquid layer is morepreferably 1×10⁻³ Pa·s or more, still more preferably 1×10⁻² Pa·s ormore, and also is more preferably 1×10² Pa·s or less, still morepreferably 1×10 Pa·s or less.

The surface tension at 25° C. of the liquid layer is more preferably 20mN/m or more, still more preferably 30 mN/m or more.

The viscosity of the liquid layer can be measured by a rotationalviscometer, etc.

The surface tension of the liquid layer can be measured by a ringmethod, etc.

If the vapor pressure of the liquid layer is too high, the liquid layermay evaporate, resulting in failing to function as a glass sheetcomposite. Accordingly, the vapor pressure at 25° C. and 1 atm of theliquid layer is preferably 1×10⁴ Pa or less, more preferably 5×10³ Pa orless, still more preferably 1×10³ Pa or less. In the case where thevapor pressure is high, sealing, etc. may be applied so as to preventthe liquid layer from evaporating, but in that case, the sealingmaterial should not hinder the vibration of the glass sheet composite.

In view of high rigidity maintenance and vibration transfer, a smallerthickness of the liquid layer is more preferred. Specifically, when thetotal thickness of the pair of glass sheets is 1 mm or less, thethickness of the liquid layer is preferably 1/10 or less, morepreferably 1/20 or less, still more preferably 1/30 or less, yet stillmore preferably 1/50 or less, even still more preferably 1/70 or less,even yet still more preferably 1/100 or less, of the total thickness ofthe pair of glass sheets.

In the case where the total thickness of the pair of glass sheets ismore than 1 mm, the thickness of the liquid layer is preferably 100 μmor less, more preferably 50 μm or less, still more preferably 30 μm orless, yet still more preferably 20 μm or less, even still morepreferably 15 μm or less, even yet still more preferably 10 μm or less.

The lower limit of the thickness of the liquid layer is preferably 0.01μm or more in view of film-forming property and durability.

It is preferred that the liquid layer is chemically stable and areaction does not occur between the liquid layer and a pair of glasssheets located on both sides of the liquid layer. The “chemicallystable” means, for example, to undergo little degradation(deterioration) by light irradiation or not to cause solidification,vaporization, decomposition, discoloration, chemical reaction withglass, etc. at least in a temperature region of −20 to 70° C.

The component of the liquid layer includes, specifically, water, oil, anorganic solvent, a liquid polymer, an ionic liquid, a mixture thereof.

More specifically, the component includes propylene glycol, dipropyleneglycol, tripropylene glycol, straight silicone oil (dimethyl siliconeoil, methyl phenyl silicone oil, methyl hydrogen silicone oil),denatured silicone oil, an acrylic acid-based polymer, liquidpolybutadiene, glycerin paste, a fluorine-based solvent, a fluororesin,acetone, ethanol, xylene, toluene, water, mineral oil, and a mixturethereof. Among these, it is preferable to contain at least one memberselected from the group consisting of propylene glycol, dimethylsilicone oil, methyl phenyl silicone oil, methyl hydrogen silicone oil,and denatured silicone oil, and it is more preferable to containpropylene glycol or silicone oil as a main component.

In addition, a slurry having dispersed therein a powder may also be usedas the liquid layer. From the viewpoint of enhancing the losscoefficient, the liquid layer is preferably a uniform fluid, but in thecase of imparting design or functionality such as coloration orfluorescence to the glass sheet composite, the slurry is effective.

The content of the powder in the liquid layer is preferably from 0 to 10vol %, more preferably from 0 to 5 vol %.

From the viewpoint of preventing sedimentation, the particle diameter ofthe powder is preferably from 10 nm to 1 μm, more preferably 0.5 μm orless.

In addition, from the viewpoint of imparting design and functionality,the liquid layer may contain a fluorescent material. The liquid layermay be either a slurry-like liquid layer in which a fluorescent materialis dispersed as a powder, or a uniform liquid layer in which afluorescent material is mixed as a liquid. Because of thisconfiguration, an optical function such as light absorption or lightemission can be imparted to the glass sheet composite.

(Glass Sheet)

In the glass sheet composite (10) according to the present invention, atleast a pair of glass sheets are preferably provided to sandwich theliquid layer (16) from both sides (FIG. 1). Denoting one glass sheet asglass sheet A (11) and the other as glass sheet B (12), when the glass Aresonates, the presence of the liquid layer can prevent glass sheet Bfrom resonating or can damp resonant vibration of glass sheet B, so thatthe glass sheet composite can increase the loss coefficient, compared toglass sheets alone.

Out of two glass sheets constituting the pair of glass sheets, the peaktop value of resonant frequency of one glass sheet A preferably differsfrom that of another glass sheet B, and it is more preferable that theranges of resonant frequencies do not overlap each other. However, evenwhen the ranges of resonant frequencies of glass sheet A and glass sheetB overlap each other or the peak top value is the same, at the time ofresonation of one glass sheet, the vibration of the other glass sheet isnot synchronized due to the presence of the liquid layer, and theresonation is thereby canceled to a certain extent, so that a high losscoefficient can be obtained, compared with glass sheets alone.

More specifically, denoting Qa and wa respectively as the resonantfrequency (peak top) and the half-width of resonance amplitude of glasssheet A and denoting Qb and wb respectively as the resonant frequency(peak top) and the half-width of resonance amplitude of the other glasssheet B, it is preferable to satisfy the relationship of the following[formula 1]:(wa+wb)/2<|Qa−Qb|  [formula 1](wa+wb)/1<|Qa−Qb|  [formula 1]

As the value on the left side in [formula 1] is larger, the difference(|Qa−Qb|) in the resonant frequency between glass sheet A and glasssheet B becomes larger, and a high loss coefficient is advantageouslyobtained.

Accordingly, it is more preferable to satisfy the following [formula1′], and it is still more preferable to satisfy the following [formula1″]:(wa+wb)/2<|Qa−Qb|  [formula 1′](wa+wb)/1<|Qa−Qb|  [formula 1″]

Incidentally, the resonant frequency (peak top) of glass sheet and thehalf-width of resonance amplitude can be measured by the same method asthat for the loss coefficient in the glass sheet composite.

The mass difference between glass sheet A and glass sheet B ispreferably smaller, and it is more preferred that there is no massdifference. If there is a difference in the mass of glass sheet,resonation of a lighter glass sheet can be reduced by a heavier glasssheet, but resonation of a heavier glass sheet can hardly at all bereduced by a lighter glass sheet. This is because if the mass ratio isimbalance, in principle resonant vibrations cannot be mutually canceleddue to the difference in inertial force.

The mass ratio of glass sheet A and glass sheet B, represented by (glasssheet A/glass sheet B), is preferably from 0.8 to 1.25 (from 8/10 to10/8), more preferably from 0.9 to 1.1 (from 9/10 to 10/9), still morepreferably 1.0 (10/10).

In both of glass sheet A and glass sheet B, as the thickness is smaller,the glass sheets are more readily adhered to each other via a liquidlayer, and the glass sheet can be vibrated with less energy.Accordingly, in the application as a diaphragm for loudspeakers, etc.,the smaller the glass sheet thickness, the better. Specifically, thesheet thickness of each of glass sheet A and glass sheet B is preferably15 mm or less, more preferably 10 mm or less, still more preferably 5 mmor less, yet still more preferably 3 mm or less, even still morepreferably 1.5 mm or less, even yet still more preferably 0.8 mm orless. On the other hand, if the thickness is too small, n effects ofsurface defects of the glass sheet are likely to be revealed, andcracking occurs more easily, or a strengthening treatment is difficultto apply. For this reason, the thickness is preferably 0.01 mm or more,more preferably 0.05 mm or more.

In addition, in the application as an opening member for buildings andvehicles, which reduces occurrence of an abnormal noise attributed to aresonance phenomenon, the sheet thickness of each of glass sheet A andglass sheet B is preferably from 0.5 to 15 mm, more preferably from 0.8to 10 mm, still more preferably from 1.0 to 8 mm.

In the application as a glass substrate for magnetic recording mediums,of which vibration absorbing effect is enhanced, the sheet thickness ofeach of glass sheet A and glass sheet B is preferably from 0.3 to 1.2mm, more preferably from 0.4 to 1.0 mm, still more preferably from 0.5to 0.8 mm.

In the preferred application as a diaphragm, either glass sheet A orglass sheet B or both preferably have a high loss coefficient, becauseincreased vibration damping is achieved by the glass sheet composite.Specifically, the loss coefficient at 25° C. of the glass sheet ispreferably 1×10⁻⁴ or more, more preferably 3×10⁻⁴ or more, still morepreferably 5×10⁻⁴ or more. The upper limit is not particularly limitedbut is preferably 5×10⁻³ or less in view of productivity andmanufacturing cost. It is more preferred that both of glass sheet A andglass sheet B have the above-described loss coefficient.

Incidentally, the loss coefficient of the glass sheet can be measured bythe same method as that for the loss coefficient of the glass sheetcomposite.

In the preferred application as a diaphragm, either glass sheet A orglass sheet B or both preferably has a high longitudinal wave acousticvelocity in the sheet thickness direction, because the soundreproducibility in a high-frequency region is enhanced. Specifically,the longitudinal wave acoustic velocity of the glass sheet is preferably5.5×10³ m/s or more, more preferably 5.7×10³ m/s or more, still morepreferably 6.0×10³ m/s or more. The upper limit is not particularlylimited but is preferably 7.0×10³ m/s or less in view of theproductivity of glass sheet and the raw material cost. It is morepreferred that both of glass sheet A and glass sheet B satisfy theabove-described acoustic velocity.

Incidentally, the acoustic velocity of the glass sheet can be measuredby the same method as that for the longitudinal wave acoustic velocityof the glass sheet composite.

The composition of each of glass sheet A and glass sheet B is notparticularly limited but is preferably, for example, in the followingranges:

SiO₂: from 40 to 80 mass %, Al₂O₃: from 0 to 35 mass %, B₂O₃: from 0 to15 mass %, MgO: from 0 to 20 mass %, CaO: from 0 to 20 mass %, SrO: from0 to 20 mass %, BaO: from 0 to 20 mass %, Li₂O: from 0 to 20 mass %,Na₂O: from 0 to 25 mass %, K₂O: from 0 to 20 mass %, TiO₂: from 0 to 10mass %, and ZrO₂: 0 to 10 mass %, provided that the composition aboveaccounts for 95 mass % or more of the entire glass.

The composition of each of glass sheet A and glass sheet B is morepreferably in the following ranges:

SiO₂: from 55 to 75 mass %, Al₂O₃: from 0 to 25 mass %, B₂O₃: from 0 to12 mass %, MgO: from 0 to 20 mass %, CaO: from 0 to 20 mass %, SrO: from0 to 20 mass %, BaO: from 0 to 20 mass %, Li₂O: from 0 to 20 mass %,Na₂O: from 0 to 25 mass %, K₂O: from 0 to 15 mass %, TiO₂: from 0 to 5mass %, and ZrO₂: 0 to 5 mass %, provided that the composition aboveaccounts for 95 mass % or more of the entire glass.

As the specific gravity is smaller in both glass sheet A and glass sheetB, the glass sheet can be vibrated with less energy. Specifically, thespecific gravity of each of glass sheet A and glass sheet B ispreferably 2.8 or less, more preferably 2.6 or less, still morepreferably 2.5 or less. The lower limit is not particularly limited butis preferably 2.2 or more.

When the specific modulus, which is a value obtained by dividing theYoung's modulus of both glass sheet A and glass sheet B by the densitythereof, is larger, the rigidity of the glass sheet can be increased.Specifically, the specific modulus of each of glass sheet A and glasssheet B is preferably 2.5×10⁷ m²/s² or more, more preferably 2.8×10⁷m²/s² or more, still more preferably 3.0×10⁷ m²/s² or more. The upperlimit is not particularly limited but is preferably 4.0×10⁷ m²/s² orless.

(Glass Sheet Composite)

In the glass sheet composite, a higher loss coefficient is preferred,because more increased vibration damping is achieved. The losscoefficient at 25° C. of the glass sheet composite according to thepresent invention is 1×10′ or more, preferably 2×10⁻² or more, morepreferably 5×10⁻² or more.

In addition, since a higher acoustic velocity leads to enhancement ofreproducibility of high-frequency sound in a diaphragm formed, thelongitudinal wave sound velocity in the sheet thickness direction of theglass sheet composite is preferably 5.5×10³ m/s or more, more preferably5.7×10³ m/s or more, still more preferably 6.0×10³ m/s or more. Theupper limit is not particularly limited but is preferably 7.0×10³ m/s orless.

When the linear transmittance of the glass sheet composite is high,application as a translucent member becomes possible. Accordingly, thevisible light transmittance determined in conformity with JapaneseIndustrial Standards (JIS R3106-1998) is preferably 60% or more, morepreferably 65% or more, still more preferably 70% or more.

Incidentally, the translucent member includes, for example, atransparent loudspeaker, a transparent microphone, an opening member forbuildings and vehicles, and other applications.

In order to increase the transmittance of the glass sheet composite, itis also useful to match the refractive indices. More specifically, therefractive indices of glass sheet and liquid layer constituting theglass sheet composite are preferably closer, because reflection andinterference at the interface are prevented. Above all, the differencebetween the refractive index of the liquid layer and the refractiveindex of each of the pair of glass sheets in contact with the liquidlayer is preferably 0.2 or less, more preferably 0.1 or less, still morepreferably 0.01 or less.

At least one glass sheet or the liquid layer constituting the glasssheet composite can also be colored. This is useful in the case where adesign pattern or functionality such as IR cut, UV cut and privacy glassis desired for the glass sheet composite.

The glass sheets constituting the glass sheet composite may besufficient if two or more sheets are used, but three or more glasssheets may also be used (FIG. 2). A glass sheet having a differentcomposition may be used in the case of two sheets in glass sheet A andglass sheet B, and in the case of three or more sheets, glass sheet A,glass sheet B and glass sheet C (13); the same composition may be usedfor all glass sheets; or glass sheets having the same composition and aglass sheet having a different composition may be used in combination.Among others, two or more kinds of glass sheets differing in thecomposition are preferably used in view of vibration damping.

Similarly, as to the mass and thickness, the glass sheets may be alldifferent, may be all the same, or some may be different. Above all, inview of vibration damping, all of the constituent glass sheetspreferably have the same mass.

A physically strengthened glass sheet or a chemically strengthened glasssheet may also be used as at least one glass sheet constituting theglass sheet composite. This is useful in preventing breaking of theglass sheet composite. When an increase in the strength of the glasssheet composite is desired, the physically strengthened glass sheet orchemically strengthened glass sheet is preferably used for the glasssheet located on the outermost surface of the glass sheet composite, andit is more preferred that all of the constituent glass sheets are thephysically strengthened glass sheet or strengthened glass sheet.

In addition, from the viewpoint of increasing the longitudinal waveacoustic velocity or strength, it is also useful to use crystallizedglass or phase-separated glass as the glass sheet. Above all, when anincrease in the strength of the glass sheet composite is desired,crystallized glass or phase-separated glass is preferably used for theglass sheet located on the outermost surface of the glass sheetcomposite.

On at least one outermost surface of the glass sheet composite, acoating (21) or a film (22) may be formed as long as the effects of thepresent invention are not impaired (FIG. 3). The application of acoating or attachment of a film is suitable for scratch protection, etc.

The thickness of the coating or film is preferably ⅕ or less of thesheet thickness of the glass sheet of the surface layer. Aconventionally known material can be used for the coating or film, andthe coating includes, for example, a water-repellent coating, ahydrophilic coating, a water sliding coating, an oil-repellent coating,a light reflection preventive coating, and a heat shielding coating. Thefilm may include, for example, a glass anti-shatter film, a color film,a UV cut film, an IR cut film, a heat-shielding film, and anelectromagnetic wave shielding film.

The shape of the glass sheet composite can be appropriately designedaccording to use and may be a flat plate-like shape or a curved surfaceshape.

In order to raise the output sound pressure level in a low-frequencyrange, a structure in which an enclosure or a baffle plate is attachedto the glass sheet composite may also be adopted. Although the materialof the enclosure or baffle plate is not particularly limited, it ispreferable to use the glass sheet composite of the present invention.

On at least one outermost surface of the glass sheet composite, a frame(30) may be provided as long as the effects of the present invention arenot impaired (FIGS. 4, 5 a and 5 b). The frame is useful when it isdesired to enhance the rigidity of the glass sheet composite or tomaintain a curved surface shape. As the material of the frame, aconventionally known material may be used, and for example, ceramic andsingle crystal materials such as Al₂O₃, SiC, Si3N4, AlN, mullite,zirconia, yttria and YAG, metal and alloy materials such as steel,aluminum, titanium, magnesium, and tungsten carbide, a compositematerial such as FRP, a resin material such as acryl and polycarbonate,a glass material, and wood may be used.

The weight of the frame used is preferably 20% or less, more preferably10% or less, of the weight of the glass sheet.

Incidentally, a seal material (31) may also be provided between theglass sheet composite and the frame, and the liquid layer can thereby beprevented from leaking through the frame.

At least part of the outer circumferential edge surface of the glasssheet composite may be sealed by a member not hindering vibration of theglass sheet composite (FIG. 6). As the seal material (31), highlyelastic rubber, resin, gel, etc. may be used.

The resin that can be used for the seal material includes, for example,acrylic, cyanoacrylate-based, epoxy-based, silicone-based,urethane-based and phenolic resins. The curing method includesone-component type, two-component mixing type, heat curing, ultravioletcuring, and visible light curing.

A thermoplastic resin (hot-melt bond) may also be used. Examples thereofinclude an ethylene vinyl acetate-based, polyolefin-based,polyamide-based, synthetic rubber-based, acrylic and polyurethane-basedresins.

As to the rubber, for example, natural rubber, synthetic natural rubber,butadiene rubber, styrene⋅butadiene rubber, butyl rubber, nitrilerubber, ethylene⋅propylene rubber, chloroprene rubber, acrylic rubber,chlorosulfonated polyethylene rubber (hypalon), urethane rubber,silicone rubber, fluoro rubber, ethylene⋅vinyl acetate rubber,epichlorohydrin rubber, polysulfide rubber (Thiokol), and hydrogenatednitrile rubber can be used.

If the thickness t of the seal material is too small, sufficientstrength cannot be ensured, whereas if it is too large, the vibrationmay be hindered. Accordingly, the thickness of the seal material ispreferably 10 μm or more and 5 times or less the total thickness of theglass composite, more preferably 50 μm or more and smaller than thetotal thickness of the glass composite.

In order to, for example, prevent separation at the interface betweenthe glass sheet and the liquid layer of the glass sheet composite, atleast part of the surfaces of the facing glass sheets may be coated withthe seal material 31 above as long as the effects of the presentinvention are not impaired (FIGS. 7a, 7b, 8a and 8b ). In this case, thearea of the seal material-coated part is preferably 20% or less, morepreferably 10% or less, still more preferably 5% or less, of the area ofthe liquid layer so as not to hinder the vibration.

Furthermore, in order to enhance the sealing performance, the edgeportion of the glass sheet may also be processed into an appropriateshape. For example, the contact area of the seal material with glass isincreased by C-chamfering (the cross-sectional shape of the glass sheetis a trapezoidal shape) or R-chamfering (the cross-sectional shape ofthe glass sheet is a substantially arc shape) of the edge part of theglass sheet at least on one side, and the adhesive strength of the sealmaterial to the glass can thereby be enhanced (FIG. 9).

The present invention also relates to a glass sheet composite includingtwo or more glass sheets and including a liquid layer between at least apair of glass sheets out of the glass sheets, in which the thickness ofthe liquid layer is 1/10 or less of the total thickness of the pair ofglass sheets when the total thickness of the pair of glass sheets is 1mm or less, and 100 μm or less when the total thickness of the pair ofglass sheets is more than 1 mm.

Preferred embodiments of this glass sheet composite are the same asthose of the glass sheet composite described above.

(Diaphragm, Opening Member, Glass Substrate for Magnetic RecordingMediums)

The present invention also relates to a diaphragm including the glasssheet composite above and a vibrator, an opening member using the glasssheet composite, and a glass substrate for magnetic recording mediumsusing the glass sheet composite.

The diaphragm can be caused to function as a loudspeaker, a microphone,an earphone, or a casing's vibrating body or casing's speaker of amobile device, etc. by disposing, for example, one or more vibrationelements or vibration detection elements (vibrators) on one side or bothsides of the glass sheet composite. In order to enhance the output soundpressure level, two or more vibration elements are preferably disposedon both sides of the glass sheet composite. In general, the position ofthe vibrators with respect to the diaphragm is preferably the centralpart of the composite, but since the material has a high acousticvelocity and a high damping performance, the vibrator may be disposed atan edge part of the glass sheet composite. Use of the diaphragmaccording to the present invention can facilitate reproduction of thesound in a high-frequency region, of which reproduction had beenconventionally difficult. In addition, the degree of freedom in thesize, shape, color, etc. of the glass sheet composite is high, and adesign can be applied, so that a diaphragm with excellent designabilitycan be obtained. Furthermore, by sampling sound or vibration by a soundcollecting microphone or a vibration detector disposed on the surface orin the vicinity of the glass sheet composite and generating vibration ofthe same phase or reverse phase in the glass sheet composite, the soundor vibration sampled can be amplified or canceled. At this time, in thecase where the sound or vibration characteristics at the sampling pointabove are caused to undergo a change based on a certain acoustictransfer function in the course of propagating to the glass compositeand an acoustic conversion transfer function is present in the glasscomposite, the vibration can be accurately amplified or canceled bycorrecting the amplitude and phase of the control signal by means of acontrol filter. At the time of constructing the control filter above,for example, the least-square (LMS) algorithm can be used.

As a more specific configuration, for example, the glass composite ofthe present invention can be used for all or at least one glass sheet ofa double glass to provide a structure where the vibration level of thesheet at the inflow side of a sonic vibration to be controlled or thesound pressure level of a space present between glasses is sampled andafter appropriate signal correction by a control filter, output to avibration element on the glass composite disposed at the outflow side ofthe sonic vibration.

This diaphragm can be utilized, for example, as a member for electronicdevices, in a full-range loudspeaker, a loudspeaker for reproducing alow-pitched sound range of 15 Hz to 200 Hz, a loudspeaker forreproducing a high-pitched sound range of 10 kHz to 100 kHz, a largeloudspeaker having a diaphragm area of 0.2 m² or more, a smallloudspeaker having a diaphragm area of 3 cm² or less, a flatloudspeaker, a cylindrical loudspeaker, a transparent loudspeaker, amobile device cover glass functioning as a loudspeaker, a TV displaycover glass, a display outputting video signals and audio signals fromthe same surface, a loudspeaker for wearable displays, an electronicdisplay device, and lighting equipment. In addition, the diaphragm canbe used as a diaphragm or vibration sensor for headphones, earphones ormicrophones.

This diaphragm can be used as an interior vibration member of transportmachinery such as vehicle, or as an in-vehicle-in-device loudspeaker andcan form, for example, a side-view mirror, a sun visor, an instrumentpanel, a dashboard, a ceiling, a door, or other interior panels, eachfunctioning as a loudspeaker. In addition, such a member can also becaused to function as a microphone and a diaphragm for active noisecontrol.

With respect to other uses, the diaphragm can be used as a diaphragm forultrasonic generators, a slider for ultrasonic motors, a low frequencygenerator, a vibrator for propagating sonic vibration in liquid, a watertank and a container each using the vibrator, a vibration element, avibration detection element, and an actuator material for vibrationdamping equipment.

The opening member includes, for example, an opening member used forbuildings, ⋅transport machinery, etc. For example, in the case of usinga glass sheet composite less likely to resonate in the frequency band ofnoise generated from the drive part, etc. of vehicles, airplanes, ships,power generators, etc., an excellent effect of inhibiting generation ofparticularly such noise can be obtained. In addition, a function such asIR cut, UV cut and coloration can be imparted to the glass sheetcomposite.

At the time of application as an opening member, a diaphragm in whichone or more vibration elements or vibration detection elements(vibrators) are disposed on one side or both sides of the glass sheetcomposite can be caused to function as a loudspeaker or a microphone.Use of the glass sheet composite according to the present invention canfacilitate reproduction of the sound in a high-frequency region, ofwhich reproduction had been conventionally difficult. In addition, thedegree of freedom in the size, shape, color, etc. of the glass sheetcomposite is high, and a design can be applied, so that an openingmember also having excellent designability can be obtained. Furthermore,by sampling sound or vibration by a sound collecting microphone or avibration detector disposed on the surface or in the vicinity of theglass sheet composite and generating vibration of the same phase orreverse phase in the glass sheet composite, the sound or vibrationsampled can be amplified or canceled.

More specifically, the member can be used as an in-vehicle loudspeaker,an outside-the-vehicle loudspeaker, and a windshield, side glass, rearglass, or roof glass having a sound insulating function. At this time,the structure may be configured to be capable of transmitting orblocking only a specific sonic vibration. It can also be used as avehicle window, structural member, or decorative plate that has improvedwater-repellency, snow accretion resistance, ice accretion resistance orantifouling property due to sonic vibration. Specifically, the membercan be used as an automotive window glass, mirror, lens or sensor, and acover glass thereof.

The opening member for buildings can be used as window glass, doorglass, roof glass, an interior material, an exterior material, adecorative material, a structural material, an outer wall, a soundinsulating board, a sound insulating wall, and a solar cell cover glass,each functioning as a diaphragm and a vibration detecting device. Theycan also be caused to function as a sound reflecting (reverberation)plate. Furthermore, the above-described water repellency, snow accretionresistance and antifouling property can be enhanced by the sonicvibration.

As to the glass substrate for magnetic recording mediums, a highvibration control effect can be imparted to the glass sheet compositeand therefore, this is very useful in view of suppressing fluttering ofthe substrate.

(Production Method of Glass Sheet Composite)

The glass sheet composite according to the present invention can beobtained by forming a liquid layer between a pair of glass sheets.

The method for forming a liquid layer between a pair of glass sheets isnot particularly limited and includes, for example, a method of forminga liquid layer on a surface of a glass sheet and disposing another glasssheet thereon, a method of laminating together glass sheets each havinga liquid layer formed on a surface, and a method of pouring a liquidlayer into a gap between two glass sheets.

The formation of the liquid layer is not particularly limited as welland includes, for example, coating, spraying, etc. of a glass sheetsurface with a liquid constituting the liquid layer.

EXAMPLES

The present invention is specifically described below by referring toExamples, but the present invention is not limited thereto.

<Evaluation Method>

(Young's Modulus, Longitudinal Wave Acoustic Velocity, Density)

The Young's modulus E and acoustic velocity V of the glass sheet and thelongitudinal wave acoustic velocity V of the glass sheet composite weremeasured at 25° C. by an ultrasonic pulse method described in JapaneseIndustrial Standards (JIS-R1602-1995) by using a test piece having alength of 60 mm, a width of 12 mm, and a thickness of 0.5 to 1 mm(DL35PLUS, manufactured by Olympus Corporation was used). As for thelongitudinal wave acoustic velocity of the glass sheet composite, theacoustic velocity in the sheet thickness direction was measured.

The density p of the glass sheet was measured at 25° C. by theArchimedes method (“AUX320”, manufactured by Shimadzu Corporation).

(Resonant Frequency)

The loss coefficients of the glass sheet and glass sheet composite weremeasured at 25° C. using the same test piece as in the measurement aboveby means of a resonance-type internal friction measuring apparatus(“JE-HT” manufactured by Nihon Techno-Plus Corporation). Specifically,an AC voltage in the band of 600 to 3,000 Hz was continuously applied tothe test piece so as to bend the glass substrate and cause freevibration in the primary mode, and the change of vibration amplitude wasmeasured. The frequency at which the vibration amplitude h becomesmaximum was defined as the resonant frequency f.

(Loss Coefficient)

As for the loss coefficient, using the resonant frequency f of thematerial determined in the measurement above and the frequency width Wat a point decreased by −3 dB from the maximum amplitude (namely, thepoint of maximum amplitude −3 [dB]), the value represented by W/f wasdefined as the loss coefficient.

With respect to a test piece to which the method above cannot be appliedfor the reason of, for example, having a non-symmetric peak shape, inthe resonant frequency measurement, the damping time of vibrationamplitude upon stopping of vibration from a resonance state wasmeasured, and the loss coefficient was calculated using the dampingtime.

(Viscosity Coefficient)

The viscosity coefficient of the liquid layer was measured at 25° C. bymeans of a rotational viscometer (RVDV-E, manufactured by BROOKFIELD).

(Surface Tension)

The surface tension of the liquid layer was measured by the followingmethod.

A metal ring hung in parallel to a test liquid at 25° C. was sunk intothe liquid, and the ring was then gradually pulled up in the verticaldirection. At this time, the peak of the force applied by the liquidmembrane was measured to calculate the surface tension.

Example 1

Glass sheet 1 of 12 mm×60 mm×0.5 mm was prepared as glass sheet A andcoated with ion-exchanged water as a liquid layer and furthermore, glasssheet 2 of 12 mm×60 mm×0.5 mm was adhered thereto as glass sheet B toobtain a glass sheet composite of 12 mm×60 mm×1 mm. The compositions(mass %) and the physical property values of glass sheet 1 and glasssheet 2 are as follows: (glass sheet 1) SiO₂: 60%, Al₂O₃: 17%, B₂O₃: 8%,MgO: 3%, CaO: 4%, SrO: 8%, density: 2.5 g/cm³, Young's modulus: 77 GPa,specific modulus: 3.1×10⁷ m²/s²; (glass sheet 2) SiO₂: 61.5%, Al₂O₃:20%, B₂O₃: 1.5%, MgO: 5.5%, CaO: 4.5%, SrO: 7%, density: 2.7 g/cm³,Young's modulus: 85 GPa, specific modulus: 3.2×10⁷ m²/s².

Examples 2 to 12

Glass sheet composites were obtained in the same manner as in Example 1except for changing the liquid layer. Incidentally, as for Example 6,glass sheet 1 was used in place of glass sheet 2 as glass sheet B.

Comparative Examples 1 to 4

As glass sheet A, each of glass sheet 1 (comparative Example 1), glasssheet 2 (Comparative Example 2), acrylic resin (Comparative Example 3),and alumina sintered body (Comparative Example 4) was used alone andevaluated for various properties.

Comparative Examples 5 and 6

Glass sheet B was adhered to glass sheet A without using a liquid layerto obtain a glass sheet composite (Comparative Example 5). Also, glasssheet A and glass sheet B were fusion-bonded by heating the glass sheetcomposite obtained in Comparative Example 5 at 900° C. in an airatmosphere to obtain a glass sheet composite (Comparative Example 6).

Comparative Examples 7 to 10

Glass sheet composites in which glass sheet A and glass sheet B werefixed using various adhesives or films in place of a liquid layer wereobtained.

Configurations and evaluation results of glass sheet composites obtainedin Examples 1 to 12 are shown in Table 1, and configurations andevaluation results of glass sheet composites obtained in ComparativeExamples 1 to 10 are shown in Table 2. In the Tables, 10{circumflex over( )}-2 denoted by * indicates a numeric unit of 10⁻².

TABLE 1 Liquid Couplant Example 1 2 3 4 5 6 Glass sheet A glass sheet 1glass sheet 1 glass sheet 1 glass sheet 1 glass sheet 1 glass sheet 1Sheet thickness mm 0.5 0.5 0.5 0.5 0.5 0.5 Glass sheet B glass sheet 2glass sheet 2 glass sheet 2 glass sheet 2 glass sheet 2 glass sheet 1Sheet thickness mm 0.5 0.5 0.5 0.5 0.5 0.5 Couplant H₂O glycerin +glycerin + glycerin + propylene propylene pure water pure water purewater glycol glycol Layer thickness/μm <5 <5 <5 <5 <5 <5 Viscositycoefficient mPa · s 1.2 1.9 4.1 12 48 48 Surface tension mN/m 73 68 7169 36 36 Double glass structure 2 sheets 2 sheets 2 sheets 2 sheets 2sheets 2 sheets Sheet thickness mm 1.0 1.0 1.0 1.0 1.0 1.0 Longitudinalwave acoustic 6.1 × 10³ 6.1 × 10³ 6.1 × 10³ 6.1 × 10³ 6.1 × 10³ 6.0 ×10³ velocity m/s Loss coefficient * 10{circumflex over ( )}−2 3.2 4.56.2 6.4 3.1 2.0 Liquid Couplant Example 7 8 9 10 11 12 Glass sheet Aglass sheet 1 glass sheet 1 glass sheet 1 glass sheet 1 glass sheet 1glass sheet 1 Sheet thickness mm 0.5 0.5 0.5 0.5 0.5 0.5 Glass sheet Bglass sheet 2 glass sheet 2 glass sheet 2 glass sheet 2 glass sheet 2glass sheet 2 Sheet thickness mm 0.5 0.5 0.5 0.5 0.5 0.5 Couplantethanol silicone oil silicone oil silicone oil silicone oil silicone oilLayer thickness/μm <5 <5 <5 <5 <5 <5 Viscosity coefficient mPa · s 0.7100 500 3000 10000 60000 Surface tension mN/m 22 21 21 21 21 21 Doubleglass structure 2 sheets 2 sheets 2 sheets 2 sheets 2 sheets 2 sheetsSheet thickness mm 1.0 1.0 1.0 1.0 1.0 1.0 Longitudinal wave acoustic6.0 × 10³ 6.3 × 10³ 6.2 × 10³ 6.2 × 10³ 6.1 × 10³ 6.2 × 10³ velocity m/sLoss coefficient * 10{circumflex over ( )}−2 1.6 2.0 3.1 4.1 3.9 1.7

TABLE 2 Single Sheet No Couplant Comparative Example 1 2 3 4 5 6 Glasssheet A glass sheet 1 glass sheet 2 acryl resin alumina glass sheet 1glass sheet 1 sintered body Sheet thickness mm 0.5 0.5 0.5 0.5 0.5 0.5Glass sheet B — — — — glass sheet 2 glass sheet 2 Sheet thickness mm — —— — 0.5 0.5 Couplant single sheet single sheet single sheet single sheetnone fusion-bonded at 900° C. Layer thickness/μm — — — — — — Viscositycoefficient mPa · s — — — — — — Surface tension mN/m — — — — — — Doubleglass structure — — — — 2 seats 2 seats Sheet thickness mm — — — — 1.01.0 Longitudinal wave acoustic 6.1 × 10³ 6.3 × 10³ 2.7 × 10³ 2.0 × 10⁴ —6.1 × 10³ velocity m/s Loss coefficient * 10{circumflex over ( )}−2 0.07  0.07 2.2  0.05  0.14  0.06 Solid Couplant Comparative Example 7 89 10 Glass sheet A glass sheet 1 glass sheet 1 glass sheet 1 glass sheet1 Sheet thickness mm 0.5 0.5 0.2 0.1 Glass sheet B glass sheet 2 glasssheet 2 glass sheet 1 glass sheet 1 Sheet thickness mm 0.5 0.5 0.5 0.5Couplant grease (paraffin) acrylic adhesive polyimide polyimide Layerthickness/μm 8   <5   6   25   Viscosity coefficient mPa · s — — — —Surface tension mN/m — — — — Double glass structure 2 seats 2 seats 2seats 2 seats Sheet thickness mm 1.0 1.0 0.7 0.6 Longitudinal waveacoustic 5.9 × 10³ 6.0 × 10³ — 6.0 × 10³ velocity m/s Loss coefficient *10{circumflex over ( )}−2  0.06  0.13  0.05  0.06

In all of glass sheet composites of Examples 1 to 12 having a viscositycoefficient of 0.7 mPa·s to 60 Pa·s and a surface tension of 21 to 73mN/m, in which the thickness of the liquid layer was less than 5 μm and1/10 or less of the total thickness of the pair of glass sheets, thelongitudinal wave acoustic velocity in the sheet thickness direction was6.0×10³ m/s or more, and the loss coefficient at 25° C. was 1.7×10⁻² ormore, revealing good properties.

Incidentally, a glass sheet composite in which the combination of glasssheet A and glass sheet B as a pair of glass sheets is a combination ofdifferent kinds of glass sheets (glass sheet 1+glass sheet 2) exhibitedbetter vibration damping property than that using a combination of thesame kind of glass sheets (glass sheet 1+glass sheet 1) (see, forexample, Examples 5 and 6).

On the other hand, in the case of using a single glass sheet or analuminum sintered body (Comparative Examples 1, 2 and 4), thelongitudinal wave acoustic velocity was 6.0×10³ m/s or more in allcases, but the loss coefficient at 25° C. was low, 1×10⁻³ or less, andthe composite was not suited to be a diaphragm. In the case of using anacrylic resin (Comparative Example 3), the loss coefficient at 25° C.was 2.2×10⁻², but the longitudinal wave acoustic velocity was low,2.7×10³ m/s.

In the case of not using a couplant (Comparative Example 5), the losscoefficient at 25° C. was low, 1.4×10⁻³, and the acoustic wave could notbe sufficiently transmitted between glass substrates, revealing that thecomposite is not suited to be a diaphragm. In the case of glass sheet Aand glass sheet B fuse-bonded at 900° C. (Comparative Example 6), theloss coefficient was low, similar to the single sheet.

In the case of using a solid couplant and setting its film thickness tobe 25 μm or less and 1/10 or less of the total thickness of the pair ofglass sheets (Comparative Examples 7 to 10), the loss coefficient waslow in all cases, and the composites were not suited to be a diaphragm.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope of the invention. This applicationis based on Japanese Patent Application (Patent Application No.2016-75928) filed on Apr. 5, 2016, Japanese Patent Application (PatentApplication No. 2016-174801) filed on Sep. 7, 2016, and Japanese PatentApplication (Patent Application No. 2016-228372) filed on Nov. 24, 2016,the contents of which are incorporated herein by way of reference.

INDUSTRIAL APPLICABILITY

The glass sheet composite according to the present invention has a largelongitudinal wave acoustic velocity and a high loss coefficient and istherefore suitably usable, for example, as a diaphragm used forloudspeakers, microphones, earphones, mobile devices, etc., as anopening member for buildings⋅vehicles, and as a glass substrate formagnetic recording mediums.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

-   10 Glass sheet composite-   11 Glass sheet A-   12 Glass sheet B-   13 Glass sheet C-   16 Liquid layer-   21 Coating-   22 Film-   30 Frame-   31 Seal material

The invention claimed is:
 1. A glass sheet composite having a losscoefficient at 25° C. of 1×10⁻² or more and a longitudinal wave acousticvelocity in a sheet thickness direction of 5.5×10³ m/s or more.
 2. Theglass sheet composite according to claim 1, comprising two or more glasssheets and a liquid layer between at least a pair of glass sheets-out ofthe glass sheets.
 3. The glass sheet composite according to claim 2,wherein a thickness of the liquid layer is 1/10 or less of a totalthickness of the pair of glass sheets when the total thickness of thepair of glass sheets is 1 mm or less, and 100 μm or less when the totalthickness of the pair of glass sheets is more than 1 mm.
 4. The glasssheet composite according to claim 2, wherein the liquid layer has aviscosity coefficient at 25° C. of 1×10⁻⁴ to 1×10³ Pa·s and a surfacetension at 25° C. of 15 to 80 mN/m.
 5. The glass sheet compositeaccording to claim 2, wherein both of at least a pair of glass sheetsout of all the glass sheets have a specific modulus of 2.5×10⁷ m²/s² ormore.
 6. The glass sheet composite according to claim 2, wherein out oftwo glass sheets constituting the pair of glass sheets, denoting Qa andwa respectively as a resonant frequency and a half-width of resonanceamplitude of one glass sheet A and denoting Qb and wb respectively as aresonant frequency and a half-width of resonance amplitude of the otherglass sheet B, Qa, wa, Qb and wb satisfy a relationship:(wa+wb)/4<|Qa−Qb|.
 7. The glass sheet composite according to claim 2,wherein a mass ratio of two glass sheets constituting the pair of glasssheets is from 0.8 to 1.25.
 8. The glass sheet composite according toclaim 2, wherein a sheet thickness of each of two glass sheetsconstituting the pair of glass sheets is from 0.01 to 15 mm.
 9. Theglass sheet composite according to claim 2, wherein the liquid layercomprises at least one member selected from the group consisting ofpropylene glycol, dimethyl silicone oil, methyl phenyl silicone oil,methyl hydrogen silicone oil, and denatured silicone oil.
 10. The glasssheet composite according to claim 2, comprising three or more glasssheets.
 11. The glass sheet composite according to claim 2, wherein atleast one glass sheet or the liquid layer is colored.
 12. The glasssheet composite according to claim 2, wherein the liquid layer comprisesa fluorescent material.
 13. The glass sheet composite according to claim2, wherein a difference between a refractive index of the liquid layerand the refractive index of each of the pair of glass sheets is 0.2 orless.
 14. The glass sheet composite according to claim 1, comprising aphysically strengthened glass sheet, a chemically strengthened glasssheet, or both.
 15. The glass sheet composite according to claim 1,wherein a visible light transmittance is 60% or more.
 16. The glasssheet composite according to claim 1, wherein a coating or a film isformed on at least one of the outermost surfaces of the glass sheetcomposite.
 17. The glass sheet composite according to claim 1, whereinthe glass sheet composite has a curved surface shape.
 18. The glasssheet composite according to claim 1, wherein at least part of an outercircumferential edge surface of the glass sheet composite is sealed by amember not hindering vibration of the glass sheet composite.
 19. Adiaphragm comprising the glass sheet composite according to claim 1 andat least one vibrator disposed on one side or both sides of the glasssheet composite.
 20. An opening member comprising the glass sheetcomposite according to claim
 1. 21. A glass substrate for magneticrecording mediums, comprising the glass sheet composite according toclaim 1.